U.S. Pat. No. 4,490,421 Levy, and U.S. Pat. No. 5,264,260, Saab, describe PET balloons. U.S. Pat. No. 4,906,244, Pinchuk et al, and U.S. Pat. No. 5,328,468, Kaneko, describe polyamide balloons. U.S. Pat. No. 4,950,239, Gahara, and U.S. Pat. No. 5,500,180, Anderson et al describe balloons made from polyurethane block copolymers. U.S. Pat. No. 5,556,383, Wang et al, and U.S. Pat. No. 6,146,356, Wang et al, describe balloons made from polyether-block-amide copolymers and polyester-block-ether copolymers. U.S. Pat. No. 6,270,522, Simhambhatla, et al, describes balloons made from polyester-block-ether copolymers of high flexural modulus. U.S. Pat. No. 5,344,400, Kaneko, describes balloons made from polyarylene sulfide. U.S. Pat. No. 5,833,657, Reinhart et al, describes balloons having a layer of polyetheretherketone. All of these balloons are produced from extruded tubing of the polymeric material by a blow-forming radial expansion process.
In mass production of medical device balloons, some processes produce substantial rejection rates. Parison shaping techniques going beyond simple axial stretching and radial expansion of straight tubes tend to increase balloon rejection rates. Grinding or necking down ends of a parison may have such an effect. Nevertheless, shaped parisons are often needed, for instance to allow large diameter balloons to be fashioned with high burst strength and/or for mounting on small diameter catheters. A free-blowing step in a balloon forming process can also display such problems.
When molding balloons utilizing engineering polymer systems like polyamide derivatives, polyethylene terephthalate, and polybutylene terephthalate, the polymer material in the proximal and distal tapered cones typically results in a much higher average wall thickness versus that of the cylindrical balloon body portion. The above-mentioned balloon cone average wall thickness is typically much higher man what is actually required to provide adequate bunt strength. The problem of excessive wall thickness in the balloon cone areas has been addressed in a variety of ways. These have included removal of material from balloon cone walls via material ablation, chemically, mechanically or otherwise, from the balloon or the parison and modifications of a balloon preform by heating and drawing selective portions of the parison or balloon precursor. Examples of such techniques include U.S. Pat. No. 5,826,588, Forman; U.S. Pat. No. 6,458,313, Hudgins et al; U.S. Pat. No. 4,963,313, Noddin et al; U.S. Pat. No. 5,017,325, Jackowski et al; U.S. Pat. No. 5,334,146, Ozasa; U.S. Pat. No. 5,525,388, Wand et al; U.S. Pat. No. 5,714,110, Wang et al; U.S. Pat. No. 5,948,345, Patel; and U.S. Pat. No. 6,193,738, Tomaschko et al.
The ability to accurately and repeatably remove or reduce material in the balloon cone regions is important to successful, low profile peripheral vascular balloon deliverability through small introducer sheaths. While balloon cone thickness can be reduced in many ways, it is often difficult to obtain consistent results, especially when using prior art material removal techniques, whether they are applied to a preform or to the formed balloon. This is especially true with larger balloons that often must be used in peripheral vascular procedures.
U.S. Pat. No. 5,714,110, Wang et al., describes a method for forming a catheter balloon comprising the steps of placing tubing of a thermoplastic material in a mold and blowing the balloon by pressurizing and tensioning the tubing while gradually dipping the mold into a heated heat transfer media so as to sequentially blow the first waist, the body and the second waist portions of the balloon, the tubing being subjected to a relatively lower pressure while the body portion is blown than while the first and second waist portions are blown.
In U.S. Pat. No. 6,572,813, Zhang et al, an apparatus is described in which a mold form is heated by mechanically moving one or more external heaters along the outside of a balloon mold containing a tubular parison. The document states that the temperature of the parison, along the effective length of the mold should be kept within a specified minimum difference, for instance 100° C. and preferably within 20° C. That is, a relatively non-uniform heating apparatus is controlled to provide a more uniform heating. In this respect the system is understood to merely mimic heating behaviour of well known balloon molding systems, for instance those in which mold forms are dipped into a heated liquid bath and those in which a block heater surroundingly contacts the mold.
In copending U.S. patent application Ser. No. 10/753,043, filed Jan. 7, 2004, there is described an apparatus for forming a medical device balloon wherein the heating system applies heat differentially to predetermined parison initiation zone and remainder zone locations on the parison so that the initiation zone location is heated to a higher temperature than the remainder zone location for at least an initiation time period encompassing the initiation of blowing of the parison.